Surface finishing processes, particularly repair processes in the automotive refinish industry, involve the application of fillers to imperfections in the surface followed by progressive abrasion with coarser to finer abrasive materials until the desired smooth surface is achieved. A series of protective coatings is applied, e.g., primer, sealers, base coats, clear coats, and so forth, and each layer is normally abraded prior to application of the next coat in order to ensure a smooth surface. A smooth surface is obtained by preferentially abrading high spots until a uniform flat aesthetically pleasing surface is obtained.
In order to assist the operator in identifying areas requiring abrasion and highlighting defects during the repair process, it is known to apply a guide coat to the surface being abraded. The guide coats generally comprise a dilute paint mixture which are sprayed over the surface to be abraded providing a light paint coating. As the surface is abraded, the guide coat is removed from the higher portions of tile surface leaving the visible guide coat on the lower areas. Thus, the surface irregularities are clearly visible to the operator, enabling the operator to abrade and fill the appropriate areas to achieve a flat high quality repair.
Various current guide coats are applied as thin coatings of liquid paint which must dry or cure before the sanding operation. Aerosol paints, which are commonly thermoplastic lacquer based materials, are convenient to use and dry quickly when compared to automotive paints or primers when used as guide coats. However, thermoplastic materials tend to load the abrasive disc during the sanding operation which decreases cut rate and disc life compared to crosslinked thermoset materials. Disadvantages of crosslinked paints or primers when used as guide coats are that they are usually multi-component, higher solids, slower drying and less convenient compared to the aerosol products.
WO 95/08405 discloses a guide coat formed on a surface as part of a smoothing operation e.g., of vehicle bodywork by distributing finely divided particulate material, e.g., a non-toxic, black powdered paint over the surface so the material remains on and thus highlights any irregularities on the surface. The material may be wiped onto the surface by an applicator e.g., synthetic foam or sponge impregnated with the material. The material may be stored in a container in a loose finely divided form or in a compact substantially solid form from which finely divided particles may be removed. The majority of the material is subsequently removed from the surface as this surface is abraded to remove the highlighted irregularities.